The Jet Propulsion Laboratory uses extremely sensitive receive systems to communicate with deep space probes and to perform radio science experiments. They incorporate sensitive high-electron mobility transistors (HEMT) or masers with very low noise temperatures as their front-end amplifiers. Radio frequency interference (RFI) can significantly degrade the performance of these receive systems. Out-of-band RFI can result in gain compression, noise temperature increases, and in the case of masers, spurious output signals. Low loss bandpass filters fabricated from high temperature superconducting (HTS) materials can provide RFI protection for these amplifiers. The low loss that these filters exhibit allow them to provide protection without significantly degrading the noise temperature or microwave performance (return loss, group delay variation, etc.) of the receive system. Superconducting Technologies Incorporated in Santa Barbara, California, designed and fabricated a 2.3 GHz (S-band) and a 8.45 GHz (X-band) bandpass filter for JPL. Both prototype filters incorporate a five-resonator, stripline structure with Tl-Ca-Ba-Cu-O thin film resonators. They were designed to have a bandwidth of 60 MHz and 150 MHz, respectively, with a desired insertion loss of less than 0.5 dB. The filters were characterized by JPL at 12 Kelvin in a closed cycle refrigerator. The lowest insertion loss measured was 0.21 dB (including connector losses) with a return loss of greater than 15 dB. The insertion loss appears to be limited by extrinsic factors such as joint losses and impedance matching, and not by the superconducting material losses.
Evaluation of an S- and an X-band HTS filter
Bewertung von Hochtemperatursupraleiter-Filter für das S-Band und X-Band
1993
6 Seiten, 7 Bilder, 6 Quellen
Conference paper
English
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